Copper-Bridged Tetrakis(4-ethynylphenyl)ethene Aggregates with Photo-Regulated 1 O2 and O2 .- Generation for Selective Photocatalytic Aerobic Oxidation.

Active species regulation is a key scientific issue that essentially determines the selectivity and activity of a photocatalyst. Herein, CuI -bridged tetrakis(4-ethynylphenyl)ethene aggregates (T4 EPE-Cu) with photo-regulated 1 O2 and O2 .- generation were demonstrated for selective photocatalytic aerobic oxidation. In this system, transient photovoltage combined with the density functional theory calculations confirmed that Cu-alkynyl was the main oxygen activation site. The adsorbed O2 tends to produce O2 .- because of the potential well effect of Cu-alkynyl under high-energy light excitation. But under low-energy light, O2 tends to produce 1 O2 via resonance energy transfer with Cu-alkynyl. For α-terpinene oxidation, the ratios of 1 O2 products to O2 .- products can be controlled from 1.3 (380 nm) to 10.7 (600 nm). Furthermore, T4 EPE-Cu exhibited ultrahigh photocatalytic performance for Glaser coupling and benzylamine oxidation, with a conversion and selectivity of over 99 %.

Carbon dots with different energy levels regulate the activity of metal-free catalyst for hydrogen peroxide photoproduction.

Artificial photoproduction of hydrogen peroxide (H2O2) from H2O and O2 by metal-free catalysts (e.g., graphitic carbon nitride) is regarded as an ultra-clean approach. Metal-free catalysts are often hindered by unpropitious rapid charge recombination and unfavorable selectivity. Herein, three carbon dots (CDs1 to CDs3) decorated modified-carbon nitride (CDs1-NCN, CDs2-NCN and CDs3-NCN) were designed and fabricated, which show diverse activity of H2O2 photoproduction. Among them, CDs1-NCN, as a two-channel photocatalyst, achieves H2O2 production with high efficiency (1938 µmol h-1 g-1). This process is at normal pressure and without sacrificial agent under visible region (λ≥420nm), which is 27.5- times higher than that of pristine C3N4. The apparent quantum efficiency can be calculated to 7.03 % (λ=365nm). In this system, CDs with different energy levels dominate the activity of metal-free catalyst for hydrogen peroxide photoproduction. Combining with photoelectrochemical test and transient photovoltage analysis, the active site and the catalytic mechanism of these composite catalysts are also clarified. Our work provides a clearly insight for understanding of the regulation of interfacial electron transport in metal-free photocatalysts.

Organic Semiconductor/Carbon Dot Composites for Highly Efficient Hydrogen and Hydrogen Peroxide Coproduction from Water Photosplitting.

Coproduction of hydrogen (H2) and hydrogen peroxide (H2O2) from water splitting is one of the most promising ways to alleviate the energy crisis and environmental pollution. Here, we first show the synthesis and photocatalytic property of an organic semiconductor (DAnTMS compound) from 9,10-dibromoanthracene and trimethylsilylacetylene. Then, a metal-free photocatalyst of a DAnTMS/carbon dot (DAnTMS/CD) composite was designed and fabricated, which achieved the efficient photocatalytic production of H2 and H2O2 without usage of any organic solvents and sacrificial agents. Under visible light, the DAnTMS/CD composite could produce H2O2 with a maximum rate of 396.7 µmol g-1 h-1 and H2 with a maximum rate of 265.0 µmol g-1 h-1 in pure water. Transient photovoltage tests showed that CDs changed the interfacial electron transfer kinetics and served as the active site for highly efficient H2 evolution. This work provided a deep insight into the function of CDs in regulating the catalytic property of organic photocatalysts.